When video information and audio information are simultaneously recorded on a recording disc, such as a video disc, in a multiplex form, a video information carrier signal having a frequency f.sub.v is, for example, angular-modulated (phase- or frequency-modulated) by the video information and an audio information carrier signal having a frequency f.sub.A is modulated in a desired modulation manner. Both of the modulated video and audio information carrier signals are superposed on each other thereby to produce a high frequency signal carrying thereon both the video and audio information which is called a RF signal. The RF signal is optically, electrostatically or otherwise recorded on the recording disc in the form of one or more tangential tracks.
In order to read and reproduce the recorded video and audio information on the recording disc, a recording disc player is used in which the recording disc is rotated at a desired rotational speed. A pickup unit is provided in the vicinity of the rotating recording disc, which optically, electrostatically or otherwise reads the recorded signal from the recording disc and produces the RF signal containing the video and audio information carrier signals. The read RF signal is separated into the original video information carrier signal and the audio information carrier signal by means of, for example, filter means. the filter means are constituted by two band pass filters respectively having central frequencies of f.sub.V and f.sub.A.
As is well known in the art, when the RF signal is read from a rotating recording disc, the RF signal contains beat frequency signals respectively having beat frequencies of f.sub.V -f.sub.A and f.sub.V +f.sub.A due to beating phenomenon. The beat frequency signals reside within both side bands of the video information carrier signal so that the filter means cannot usually separate the video information carrier signal and the beat frequencies. As long as the frequency characteristics in amplitude of the pickup means is flat with respect to the frequencies of the input signals thereof, there is no problem.
However, if the frequency characteristics in amplitude of the pickup means degrades across the video information carrier frequency/f.sub.V, the RF signal thereby produced contains spurious components which the demodulator cannot delete from the video information signal.
Being well known in the art, the pickup means is usually subjected to modulation in transfer function (MTF) with respect to space frequency which causes degradation in the frequency characteristics of the pickup means within a higher frequency region, whereby the generation of the spurious or extraneous components due to beat frequency components is unavoidable in the prior art information reproducing apparatus.
It is accordingly a primary object to provide a new and improved information reproducing apparatus for reading and reproducing an angular-modulated information carrier signal which is recorded together with another information carrier signal in a multiplex form on a rotating recording disc, which apparatus is free from the unwanted generation of the spurious components in the RF signal obtained from the recording disc.